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FNA | Family List | FNA Vol. 21 | Asteraceae | Chaenactis

11. Chaenactis macrantha D. C. Eaton in S. Watson, Botany (Fortieth Parallel). 171, plate 18, figs. 1–5. 1871.

Showy or bighead dustymaidens, Mojave pincushion

Plants 5–25(–35) cm; proximal indument grayish, arachnoid-sericeous to closely lanuginose (sometimes tardily glabrescent). Stems mostly 1–5; branches mainly proximal. Leaves basal (withering) and cauline, 1.5–7 cm; largest blades ± elliptic to ovate, ± plane, not succulent, 1(–2)-pinnately lobed (± gland-dotted beneath indument); primary lobes mostly 2–5 pairs, ± remote, ultimate lobes ± plane. Heads (± radiant, nocturnally), mostly 1–5(–7) per stem (nodding in bud). Peduncles 1.5–8 cm, arachnoid-sericeous to thinly lanuginose distally, not stipitate-glandular. Involucres ± obconic to broadly cylindric. Phyllaries: longest 12–18 mm; outer arachnoid-sericeous to thinly lanuginose in fruit, not stipitate-glandular, apices ± squarrose, blunt, pliant. Florets: corollas (nocturnal) white to pinkish or cream, 9–12(–15) mm (lengths 1.8–2.2 times cypselae; anthers ± included); peripheral corollas nocturnally spreading, actinomorphic, scarcely enlarged. Cypselae 5–6(–7) mm; pappi of 8 scales in 2, abruptly unequal series, longest scales 5–7 mm. 2n = 12.

Flowering Mar–early Jul. Open, loose, light-colored, silty, usually calcareous or alkaline, desert soils, often covered by or mixed with gravel; 600–2200 m; Ariz., Calif., Idaho, Nev., Oreg., Utah.

Though the derived floral features of Chaenactis macrantha obscure its relationships, it may represent a link between sect. Chaenactis (annuals; pappus scales in regular, often strongly reduced series) and sect. Macrocarphus (leaf blades gland-dotted). Resemblance of its heads, leaves, and indument to those of C. thompsonii and relatives is striking. It appears to form no natural hybrids, perhaps because of its nocturnal corollas.


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